Pneumatic punch with slug removing facility



United States Patent [56] References Cited UNITED STATES PATENTS 12/1939 Ehrsam 3,236,130 2/1966 Robert [72] Inventor Rubin Goldman 22 Park Drive, Newton Highlands, Massachusetts 02162 712,988

Primary Examiner Frank 'I'. Yost Attorney-Wolfe, Greenfield, and Hieken OVING Appl. No. Filed March 14, 1968 [45] Patented Aug. 18, 1970 [54] PNEUMATIC PUNCH WITH SLUG REM FACILITY 3 Claims, 1 Drawing Fig. [52] 83/123 ABSTRACT: A pneumatic punch having a punch and ac- B26d 7/06 tuator provided with internal air passages for removing slugs 83/98, from the region of the cooperating die simultaneously with the pneumatic actuation ofthe assembly.

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RUBIN GOLDMAN ATTORNEYS PNEUMATIC PUNCH WITH SLUG REMOVING FACILITY This invention relates to punching apparatus and more particularly comprises a new and improved punch assembly for perforating thin sheet stock.

In recent years polyethylene bags have been widely used to package such diverse products as food stuffs, clothing and scientific instruments. In certain of such uses, it is necessary to perforate the bags to allow air to circulate about the goods packaged in them. To form perforations most economically in the plastic sheet material of the bags, it is customary to mount on the bag making machines auxiliary equipment which will perform the punching operations while the bag making machines cut, fold and seal the edges of the sheet to form the bags.

Many of the punch assemblies available to perform the punching operations require regular sharpening of the punch and die which forms part of the apparatus, and obviously sharpening the cutting tools causes down time, which is economically wasteful. Further, many of the assemblies now available provide no means for removing the slugs cut from the sheet stock, which then collect on the stock and may contaminate the bag contents and may also interfere with the proper operation of the assembly.

One important object of this invention is to provide a punch assembly which does not require regular and frequent sharpening ofits cutting tools.

Another important object of this invention is to provide a punch assembly which provides means for positively removing slugs which are produced by perforating the sheet stock which passes through the machine.

Yet another important object of this invention is to provide a punch assembly which is free of external hoses and other forms of flexible ducts for directing an air blast to the punch and die for removing slugs.

To accomplish these and other objects, the punch assembly of this invention comprises a pneumatic cylinder carried by the assembly frame. A die is mounted on the frame. and a punch actuator is mounted on the frame as well. A punch is operatively connected to the actuator and cooperates with the die to perforate stock placed between it and the die. An air passage extends through the actuator and an opening is provided in the punch in communication with the passage so that air directed through the passage is discharged by the punch and is directed toward the die to remove any slugs which are left at that region. Means are provided for energizing the cylinder which causes the actuator to move the punch toward the die and simultaneously activate the air passages through the actuator and punch to remove the slugs.

These and other objects and features ofthis invention along with its incident advantages will be better understood and appreciated from the following detailed description of one embodiment thereof, selected for purposes of illustration and shown in the accompanying drawing in which the single figure is a side view partly in section of a punch assembly constructed in accordance with this invention.

The assembly shown in the figure includes a frame upon which are mounted, three major sub-assemblies, namely, pneumatic cylinder sub-assembly l2, punch sub-assembly l4 and die sub-assembly 16. The frame 10 is shown to be supported on a bar 18 which may form part of the main machine with which the punch assembly is used. Thus, typically the bar 18 could be part of a bag making machine, and the clamp 20 with its cooperating screws 22 retain the frame on the bar. It is evident that by loosening the screws 22 the frame may be moved along the bar 18 to any desired position.

The three major sub-assemblies are supported on separate holders 24, 26 and 28 which in turn are retained on the frame 10 by screws 30, 32 and 34 respectively. The position of holder 24 is shown to be adjustable as the hole 36 in the frame through which the screw extends is appreciably larger than the screw stem diameter. This feature enables the operator to achieve precise alignment between the pneumatic cylinder sub-assembly l2 and the punch sub-assembly I4.

The pneumatic cylinder sub-assembly 12 comprises cylinder 38 within which is slidably mounted piston 40. An O ring 42 perfects the seal between the piston and the inner surface of the cylinder, and the piston 40 in turn is connected to a piston rod 44 which is shown in the drawing to have an axial air passage 46 which extends throughout its length and which communicates with the chamber 48 in the cylinder 38 above the piston. This communication is achieved by virture of the fact that the piston rod 44 extends through the cross section of the piston 40, but it is to be understood that this same result could be achieved by providing a passage in the piston itself and connecting rod 44 to the lower end of the piston with its axial passage in communication with the passage in the piston.

The cylinder 38 is supported on the holder 24 by nut 50 which is screwed to the lower depending stem of the cylinder, as is evident in the drawings. A rubber washer 52 is disposed between the nut 50 and the bottom of the holder 24 so as to allow self centering action to take place between the cylinder and the punch sub-assembly 14. The pnuematic cylinder subassembly 12 also includes a spring return 54 disposed in the cylinder 38 below the piston 40 which urges the piston to a raised position (the position shown in the drawing).

The punch sub-assembly 14 includes the punch body 60 which is slidably mounted in bushing 62 carried on the punch holder 26. A keyway 64 in the side of the body 60 cooperates with key 66 carried on the end ofthe holder 26 to prevent the body from rotating as it moves vertically up and down in bush ing 62.

An air passage 68 provided in the body 60 is enlarged and threaded at its upper end as suggested at 70 and receives the threaded lower end of the piston rod 44. Thus, the body 60 is fixed to the rod 44 and moves vertically with it under the influence of energization of the pneumatic cylinder sub-as sembly 12. The piston rod 44 and the body 60are retained in their desired relative positions by the nut 72 and rubber washer 74. The rubber washer 74 cooperates with the rubber washer 52 to assure precise axial alignment of the piston rod 44 and the body 60. This is of course essential as the two move vertically together upon energization of the pneumatic cylinder. The washers compensate for any slight misalignment of the body 60 and the cylinder 38.

The lower end 76 of the punch body 60 is enlarged, and its lower surface 78 is countersunk as shown at 80 to receive the head 82 of screw 84. The screw is retained in the position shown by plate 86 which in turn is secured to the lower surface 74 by a number of machine screws 88, one of which is shown. The lower enlarged end 76 of the body 60 also carries a blade 90 in vertical slot 92. The blade may be of a variety of shapes and may be designed to make either a single cut or a series of short serrations in the stock introduced between the punch and die sub-assemblies, as will be explained in greater detail below.

The threaded stem 92 of screw 84 extends through the plate 86 and supports the punch 94. As is evident in the drawing, the punch is generally cylindrical in shape and has a lower serrated edge 96 which cooperates with the die button 100 to cut a hole in the sheet stock disposed between the punch and die sub-assemblies. The punch 94 has a bore that extends through its center, and the upper end of the bore is threaded to receive the threaded stem 92 of the screw. Thus, the punch 94 may be removed from the sub-assembly merely by unscrewing it.

The die sub-assembly 16 is shown in the drawing to include the die button 100 which is seated on the upper edge of adjusting screw 102. Screw 102 is threaded into the vertical internally threaded hole 104 in holder 28. Thus, the button 100 may be raised and lowered in the upper portion of the hole 104 (which is unthreaded) by screwing the screw 102 further into or out of holder 28. The adjusting screw is retained in the set position by means of the nut 106 which bears against the lower surface of holder 28.

Both the die button 100 and the adjusting screw 102 are shown to be hollow so as to provide a continuous open passage from the upper surface of the die button downwardly through the adjusting screw. Therefore. any slugs cut from sheet material placed between the punch and the die may be expelled from the region of the punch and die through the openings 108 and 110 in the die button and adjusting screw, respectively. In the drawing it will also be noted that a slot 112 is provided in holder 28, which receives the lower end of the blade 90. The screw 84 which retains the punch 94 in place has an axial opening 114 extending through it so that the passage 68 in the body 60 communicates with the passage 114 in the screw 84 and the hollow interior of the punch.

The assembly shown in the drawing is completed by an impulse valve 120 which is carried by and communicates with the interior chamber 48 of the cylinder 38. The impulse valve controls the flow of air to the chamber 48 so as to control the actuation of the piston 40 and the various parts of the assembly that move with it. When the valve is opened, air is directed into the chamber 48 to drive the piston 40 downwardly. The impulse valve 120 is connected by means of a duct 122 through gage 124 and regulator 126 to a compressed air source represented by box 128, which may be in the form of a manifold, air compressor, or any other source. The impulse valve is controlled by air from a second source 130, which communicates by means of duct 132 to pilot inlet 134 of the impulse valve. A valve 136 may be connected to the source 130 so as to effectively control the operation of the impulse valve 120. Typically the valve 136 may be a solenoid which opens and closes to open and close the impulse valve 120 by alternately supplying and discontinuing the supplying of compressed air to the control pilot 134. The impulse valve and its associated parts is of standard design and is shown in my earlier patent No. 3,299,761 issued January 24, 1967 and entitled Punch Assembly.

In operation the punch assembly functions as follows as it punches and slits a hole in the sheet stock S which typically represents a polyethylene sheet or bag At rest, the assembly is in the position shown in full lines in the drawing. in order to punch and slit the stock S, the impulse valve 120 is opened by means of the control inlet supply 132, and operating pressure is applied in the chamber 48 to drive the piston downwardly against the bias of spring 54. As the piston 40 moves downwardly in the cylinder, it carries with it the piston rods 44, the punch body 60, and the punch 94 and blade 90. Axial alignment of the various parts is preserved by means of the rubber washers 52 and 74 in the assembly. As the punch 94 and blade 90 move downwardly, they enter the die button 100 and the slot 112 as suggested in broken lines in the drawing. Approximately 1/32 of an inch clearance exists between the outer surface of the punch 94 and the inner surface of the die button so as to reduce if not entirely eliminate wear on the die button. This arrangement has an advantage over the conventional ball type punch and die button, which requires regular sharpening for effective use.

It is evident that when the punch and blade move to the positions shown in dotted lines, they will respectively form a circular hole and slit in the stock S. The formation of the circular hole produces a slug of the material cut from this stock. In accordance with this invention, simultaneously with the activation of the piston 40 in the cylinder 38, air is directed down through the passage 46 in the piston rod 44, the passage 68 in the body 60, passage 114 in screw 84, and the hollow body of the punch 94 so as to blow the slug produced by the punch through the openings 108 and 110 in the die button and adjusting screw respectively. Therefore, there is no build up of slugs in the die button which could interfere with the punch 94 or spill out on the sheet. The working area of the assembly rather is kept free of slugs by the constant air blast which is discharged through the punch during the cutting operation.

The impulse valve is operated instantaneously so that the piston 40 is driven downwardly in the cylinder by a single burst of air. Almost immediately following the introduction of air under pressure in the chamber 48, the impulse valve is closed, and the piston 40 is returned to the influence of the spring 54. In this way, the assembly is returned to the position shown in full lines. The stock then is again advanced and the next hole is punched by again opening the impulse valve 120.

It is evident that with the arrangement of this invention described and shown, the working region is kept free of slugs without the use of air hoses and other extraneous blowing devices which bend and wear through continued use of the assembly. The air passage which is formed internally in the assembly of this invention is free of all wearing parts and will not require periodic service. The punch itself which is provided with clearance within the die button is also free of wear and does not produce rapid wear of the die button which is the case when a ball-type punch is used.

From the foregoing description, those skilled in the art will appreciate that numerous modifications may be made of this invention without departing from its spirit. Therefore, I do not intend to limit the breadth of this invention to the single embodiment illustrated and described. Rather, it is intended that the scope of this invention be determined by the appended claims and their equivalents.

Iclaim:

1. A punch assembly comprising:

a frame,

a pneumatic cylinder mounted on the frame,

a die in the form ofa sleeve mounted on the frame,

a punch actuator mounted on the frame,

an air passage extending through the actuator and in communication with the pneumatic cylinder,

a punch operatively connected to the actuator and moving in and out of the sleeve to perforate stock disposed between the die and the punch, said punch having its cutting edge serrated,

an opening in the punch forming a continuation of the air passage in the actuator for discharging air directed through the passage from the cylinder to blow slugs cut from the stock through the die,

means including a duct for connecting the cylinder to a pressure source,

a pneumatic impulse valve in the duct when opened allowing the pressure source to move the actuator to drive the punch into the sleeve and simultaneously direct air through the punch to remove the slugs from the region ofthe punch and die,

a connection in the pulse valve for connecting it to a pilot line for instantaneously opening the valve,

and a spring operating on the actuator for driving the punch out ofthe sleeve when the valve is closed.

2. A punch assembly as defined in Claim 1 further characterized by said actuator including a body slidably mounted on the frame and carrying the punch with the passage extending through the body.

3. A punch assembly as defined in Claim 2 further characterized by said cylinder including a piston and piston rod with the rod connected to the body,

an opening extending through the piston and the rod and communicating with the passage in the body, said opening directing air through the passage in the body which is introduced into the cylinder to drive the piston. 

